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Antennas and Propagation, IEEE Transactions on

Issue 7 • Date July 2009

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Displaying Results 1 - 25 of 52
  • Table of contents

    Page(s): C1 - 1862
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    Freely Available from IEEE
  • IEEE Transactions on Antennas and Propagation publication information

    Page(s): C2
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    Freely Available from IEEE
  • Comparison of Antenna Measurement Facilities With the DTU-ESA 12 GHz Validation Standard Antenna Within the EU Antenna Centre of Excellence

    Page(s): 1863 - 1878
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    The primary objective of many antenna measurement facilities is to provide a specified high accuracy of the measured data. The validation of an antenna measurement facility is the process of proving that such a specified accuracy can be achieved. Since this constitutes a very challenging task, antenna measurement accuracy has been the subject of much research over many years and a range of useful measures have been introduced. Facility comparisons, together with antenna standards, error budgets, facility accreditations, and measurement procedure standards, constitute an effective measure towards facility validations. This paper documents the results of a comparison between 8 European antenna measurement facilities with a specially designed reference antenna, the DTU-ESA 12 GHz validation standard antenna (VAST-12). The electrical and mechanical properties of the VAST-12 antenna are presented and its three different coordinate systems are defined. The primary objective of the comparison is to obtain experience and results that can serve to develop standards for validation of antenna measurement facilities. The paper focuses on the comparison of the radiation pattern and presents not only the measurement data obtained at the facilities, but also investigates several procedures for comparing these data. This includes various definitions of pattern difference and statistical measures as well as a reference pattern. The comparison took place in 2004-2005 as part of the European Union network of excellence called ACE-Antenna Centre of Excellence. View full abstract»

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  • Gain and Q Bounds for Coupled TM-TE Modes

    Page(s): 1879 - 1885
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    The possibility of minimizing the bound on the Q of an antenna by resonating TM modes with TE modes has been described in many papers. Other papers have dealt with maximizing the gain by combining these modes in an optimum manner. However, there are fundamental relations for the phasing of the two modes which prevents minimum Q and maximum gain from being realized simultaneously. These phase restrictions have been neglected in some papers, leading to the presentation of incorrect results. This paper explores the relationships between phase, gain, bandwidth, and the Q lower bound, particularly for electrically-small antennas. View full abstract»

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  • Analysis of Planar Ultrawideband Antennas With On-Ground Slot Band-Notched Structures

    Page(s): 1886 - 1893
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    Planar ultrawideband (UWB) antennas with on-ground band-notched structures are studied in this paper. Two different slot resonators, which feature quarter-wavelength and half-wavelength configurations, are embedded into the arc shaped ground plane of the circular disk patch antennas in order to obtain the desired band-rejection around 5.8 GHz. Their principles and characteristics are analyzed and compared in detail providing designers with in-depth understanding and useful design information. By choosing the quarter-wavelength slot resonator, the first spurious stopband can be pushed up to 3 f 0 (f 0 stands for the center frequency of the notch) and this antenna retains a super wide working band which spans from 1.62 GHz to 17.43 GHz. Performance in both the frequency domain and time domain for this antenna has been investigated carefully. The transmission response of a transceiving antenna system and their corresponding transient analysis are discussed at the end of this paper. View full abstract»

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  • A Novel Technique for Open-Stopband Suppression in 1-D Periodic Printed Leaky-Wave Antennas

    Page(s): 1894 - 1906
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    A novel technique for the elimination of the open stopband in one-dimensional periodic printed leaky-wave antennas is presented. A quarter-wave transformer, or alternatively a matching stub, is introduced into the unit cell of the antenna, which forces the Bloch-wave impedance of the structure to remain real and non-zero at broadside. The effectiveness of the proposed technique is first demonstrated on a printed periodic microstrip leaky-wave antenna consisting of a single radiating stub per unit cell, which exhibits a significant stopband at broadside. The technique is then also applied to a structure consisting of two radiating stubs per unit cell, which is capable of mitigating, but not eliminating, the open stopband. In both cases the open stopband at broadside is completely suppressed. View full abstract»

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  • Very Broadband Extended Hemispherical Lenses: Role of Matching Layers for Bandwidth Enlargement

    Page(s): 1907 - 1913
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    The design and optimization of very broadband integrated lens antennas (ILAs) constitutes one of the future trends in lens antenna field. To this end we investigate numerically the radiation performance of millimeter wave ILAs coated with multiple anti reflection layers. We propose lens structures of moderate size (four wavelengths in diameter at the center frequency) and made from a dense dielectric material (ceramic). They are illuminated by two kinds of on-axis primary sources, namely a dielectric-loaded metallic waveguide and a patch antenna. This enables to assess the role of the lens illumination law on the performance of broadband ILAs. In particular, we demonstrate that ILAs coated with three stacked quarter wavelength matching layers exhibit a very broadband promising features. First their radiation characteristics remain very stable over a large frequency band: a 36% relative bandwidth is achieved using dielectric-loaded waveguide feeds. Secondly very high values of aperture efficiencies (beyond 91% over a 21% bandwidth) are obtained using printed feeds. The truncation effects of the ground plane and substrate of planar feeds upon the beam characteristics are also studied. We conclude that they must be taken into account at the very first stages of the design process of ILAs. View full abstract»

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  • Ultrawideband Circularly Polarized Spiral Antenna Using Integrated Balun With Application to Time-Domain Target Detection

    Page(s): 1914 - 1920
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1015 KB) |  | HTML iconHTML  

    The design of a wideband circularly polarized (CP) equiangular spiral antenna is described. Contrary to the conventional spiral antenna using the coaxial line or the vertically connected feeding structure, a tapered microstrip balun is fully integrated into one spiral arm of the proposed antenna and hence this construction can be realized completely planar. The measured results show that the return loss is better than 10 dB from 3.75 to 18.6 GHz, the axial ratio is below 3 dB from 3 to 14.5 GHz, the radiation is bidirectional with opposite polarization, and the antenna peak gain is 3.5 to 7 dBic. The time-domain characteristic of the transmitting/receiving system using the proposed ultrawideband (UWB) CP antennas is investigated by transient response. The pulse distortion is insignificant and is verified by the measured antenna performance with high signal fidelity (ges 0.89) and low variation of group delay (les 0.1 ns ). The transmitting/receiving antenna system using the proposed antennas is constructed to demonstrate the CP characterization and to detect the target position. View full abstract»

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  • Frequency Transformation of a Whistler Wave by A Collapsing Plasma Medium in a Cavity: FDTD Solution

    Page(s): 1921 - 1930
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    A whistler wave in a cavity filled with a magnetoplasma medium is strongly affected when the plasma source is switched-off. Due to such a collapse of the plasma, the whistler wave is converted to an electric- field-intensified higher frequency wave (with an order of magnitude upshift of the frequency). In principle, it is possible to transform a 2.45 GHz source radiation to 300 GHz Terahertz radiation, with significant strength of the electric field. Finite difference time domain (FDTD) technique is used to study the effect of the following parameters: the rate of collapse, spatial plasma-density profile, collision frequency as well as the switching angle. View full abstract»

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  • Analysis and Feeding of a Spiral Element Used in a Planar Array

    Page(s): 1931 - 1935
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    The operation of a previously introduced planar array consisting of square spiral radiating elements has been analyzed by both numerical simulation and a transmission line model. The numerical results show that previously unexplained narrow resonances in the active impedance of the spiral elements result from standing waves excited on the elements through coupling from other elements. The transmission line analysis confirms that the standing waves can only be established when the spiral arm lengths are simultaneously multiples of one half the operating wavelength. The standing wave is excited only by asymmetric coupling, so the resonances are strongly established only for off-broadside scan. A method to feed the unbalanced load presented by an asymmetric spiral that is immune to the narrow resonances is proposed. View full abstract»

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  • Synthetic-Functions Analysis of Large Aperture-Coupled Antennas

    Page(s): 1936 - 1943
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    The application is described the synthetic function expansion (SFX) approach to large arrays of aperture-coupled antennas. The problem is formulated in terms of coupled magnetic-field continuity integral equations (MFCIE) and electric field integral equations (EFIE), and discretized via the method of moments (MoM). The SFX is a domain-decomposition technique; on each block of the broken-down structure, functions are generated with domain over the entire block. These ldquosynthetic functionsrdquo (SF) are obtained from the solution of the electromagnetic problem for the isolated block upon specification of appropriate sources on the block bounding box, and from a further singular value decomposition (SVD)-based procedure to select the relevant terms. The complete problem is solved using the SFs as basis functions for the MoM. This results in a strong reduction of the MoM matrix size. Applications are presented to configurations of open and cavity-backed radiators. View full abstract»

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  • Fourier Synthesis of Linear Arrays Based on the Generalized Scattering Matrix and Spherical Modes

    Page(s): 1944 - 1951
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    This paper presents a novel, simple pattern synthesis procedure for linear equispaced arrays which can be characterized by a generalized scattering matrix (GSM) and whose radiated field can be expressed as a weighted sum of shifted spherical waves. It can be viewed as an extension of the classic design techniques of the Fourier series (FS) method or the Woodward-Lawson frequency sampling method, to the case in which the individual antenna elements' patterns and all interelement couplings are taken into account. The design procedure, which yields the excitations needed to achieve the desired pattern, is based on either the FS or the discrete Fourier transform (DFT) of the spherical mode expansion of the array radiated field, as well as on various properties associated to the FS or DFT coefficients. In this work, to compute the GSM of the array and the spherical mode expansion of the field, a validated hybrid full-wave methodology, based on the finite element method and rotation and translation properties of spherical waves, is used. Numerical results of different synthesized array patterns are presented for different arrays made up of dielectric resonator antennas and cavity-backed microstrip circular patches. View full abstract»

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  • Fast Iterative Method of Power Synthesis for Antenna Arrays

    Page(s): 1952 - 1962
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    A fast and simple method of power synthesis for antenna arrays of arbitrary geometry is presented. The method adopts an auxiliary function having the desired amplitude pattern and a generic phase pattern, and determines in closed form the array pattern approximating the auxiliary function in both amplitude and phase. A cost function involving the auxiliary function and the approximating pattern is minimized by modifying the phase pattern of the auxiliary function, using a simple and fast iterative technique. Once the optimal phase pattern has been found, the array pattern approximating the corresponding auxiliary function is the synthesized pattern. The proposed method allows to satisfy stringent requirements on the amplitude pattern, including multibeam synthesis and radiation suppression within large angular regions. Numerical results show the effectiveness of the algorithm and are compared to those obtained using other existing methods. In order to achieve a more significant comparison such methods have been properly modified to improve their performances. Such comparison shows that the presented algorithm allows a significant reduction of CPU time with respect to the other considered methods, as well as a weaker dependence on the starting point. Finally, the presented method is extended in such a way as to reduce the dynamic range ratio (DRR) of the array excitations. View full abstract»

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  • A Practical Simple Geometry and Gain/Phase Calibration Technique for Antenna Array Processing

    Page(s): 1963 - 1972
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    A calibration technique is proposed in this paper for an arbitrary array. This technique estimates the array sensor gain/phase and geometry with a set of simultaneous equations formed by using the MUSIC null spectrum property. Note that the technique does not use iterative calculation in estimating the array parameters and hence it has no convergent problem; however, it requires that n directions of arrival (DOAs) of signal sources to be known to calibrate the array which is perturbed n-dimensionally. The efficacy of the method is demonstrated by means of simulations and on experimental data collected with an antenna array operating in high-frequency radio band. View full abstract»

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  • Rapidly Convergent Representations for 2D and 3D Green's Functions for a Linear Periodic Array of Dipole Sources

    Page(s): 1973 - 1984
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    Hybrid spectral-spatial representations are introduced to rapidly calculate periodic scalar and dyadic Green's functions of the Helmholtz equation for 2D and 3D configurations with a 1D (linear) periodicity. The presented schemes work seamlessly for any observation location near the array and for any practical array periodicities, including electrically small and large periodicities. The representations are based on the expansion of the periodic Green's functions in terms of the continuous spectral integrals over the transverse (to the array) spectral parameters. To achieve high convergence and numerical efficiency, the introduced integral representations are cast in a hybrid form in terms of: (i) a small number of contributions due to sources located around the unit cell of interest; (ii) a small number of symmetric combinations of the Floquet modes; and (iii) an integral evaluated along the steepest descent path (SDP). The SDP integral is regularized by extracting the singular behavior near the saddle point of the integrand and integrating the extracted components in closed form. Efficient quadrature rules are established to evaluate this integral using a small number of quadrature nodes with arbitrary small error for a wide range of structure parameters. Strengths of the introduced approach are demonstrated via extensive numerical examples. View full abstract»

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  • Submillimeter Wave Frequency Selective Surface With Polarization Independent Spectral Responses

    Page(s): 1985 - 1994
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2185 KB) |  | HTML iconHTML  

    This paper reports the design, construction and electromagnetic performance of a new freestanding frequency selective surface (FSS) structure which generates coincident spectral responses for dual polarization excitation at oblique angles of incidence. The FSS is required to allow transmission of 316.5-325.5 GHz radiation with a loss les 0.6 dB and to achieve ges 30 dB rejection from 349.5-358.5 GHz. It should also exhibit crosspolarization levels below -25 dB, all criteria being satisfied simultaneously for TE and TM polarizations at 45 deg incidence. The filter consists of two identical, 30 mm diameter, 12.5 mum thick, optically flat, perforated metal screens separated by 450 mu m. Each of the ap 5000 unit cells contains two nested, short circuited, rectangular loop slots and a rectangular dipole slot. The nested elements provide a passband spectral response centered at 320 GHz in the TE and TM planes; the dipole slot increases the filter roll-off above resonance. The FSS was fabricated from silicon-on-insulator wafers using precision micromachining and plating processes including the use of deep reactive ion etching (DRIE) to pattern the individual slots and remove the substrate under the periodic arrays. Quasi-optical transmission measurements in the 250-360 GHz range yielded virtually identical copolarized spectral responses, with the performance meeting or exceeding the above specifications. Experimental results are in excellent agreement with numerical predictions. View full abstract»

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  • Nonreciprocal Phase-Shift Composite Right/Left Handed Transmission Lines and Their Application to Leaky Wave Antennas

    Page(s): 1995 - 2005
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    A new type of nonreciprocal phase-shift transmission line is proposed; it realizes the dominant right-handed mode in one direction of the power flow along the line, and the dominant left-handed mode in the opposite power direction. These right and left handed modes can have the same wave number vector at a specific frequency but there is no significant coupling effect. An equivalent circuit model is provided to explain its nonreciprocal transmission characteristics. A nonreciprocal phase-shift composite right/left handed transmission line is designed to satisfy specific performance parameters and fabricated as a ferrite microstrip line. The leaky wave radiation characteristics of the fabricated nonreciprocal line are investigated. An experiment and analyses confirm obliquely unidirectional leaky wave radiation from the line for the two different directions of the transmitted power. View full abstract»

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  • A Non-Invasive Metamaterial Characterization System Using Synthetic Gaussian Aperture

    Page(s): 2006 - 2013
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1253 KB) |  | HTML iconHTML  

    A new free-space measurement approach is presented to characterize radio frequency (RF) materials and metamaterials over a wide frequency range. In contrast to the traditional spot-focused horn pair system, the proposed technique generates a Gaussian beam with a tight spot, focused on a sample under test via a synthesis using individually measured responses. Therefore, difficulties in fabricating lenses for the conventional spot-focused horn pair are avoided altogether. In this paper, we validate the proposed technique by extracting the permittivity of a known dielectric slab, and subsequently proceed to characterize the transmission properties of metamaterial assembly. The proposed technique can be adapted for measurements in EM facilities using spherical or planar scanning capability. View full abstract»

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  • Comparison of FDTD Hard Source With FDTD Soft Source and Accuracy Assessment in Debye Media

    Page(s): 2014 - 2022
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    To radiate electromagnetic energy from a single point of a finite difference time domain (FDTD) grid, there are typically two general classes of electromagnetic wave sources; the soft source which consists of impressing a current, and the hard source which consists of impressing an electric field. The physical meaning of the soft source is well understood and its analytical solution is known, whereas there is no analytical solution for the hard source excitation. Nevertheless, many FDTD works utilize the hard source for its practicality. A novel aspect is that the derivation of a field radiated from the hard source towards the free space is identical to the field radiated from the soft source, provided that a certain relationship holds between the source excitations. This provides us with an analytical solution for the field radiated from the hard source. The assessment of accuracy is then considered for a wide band field radiated from a punctual source into frequency-dependent FDTD Debye media. The quantification of the deviation of the waveform observed in the FDTD space from the analytical solution is demonstrated. The numerical experiments with this quantification show that the waveform observed with the soft source excitation matches the one with the hard source excitation when the minimum wavelength to the spatial discretization ratio is greater than 10. It turns out that the soft source outperforms the hard source when the minimum wavelength relative to the spatial discretization is less than 10 in the case of lossless media. Equivalent accuracy is achievable for both lossless and lossy media even when the minimum wavelength to the spatial discretization ratio is lower than 10 due to the loss tangent which absorbs the spurious frequencies related to the numerical noise. View full abstract»

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  • A Study on the Stability and Numerical Dispersion of the Lumped-Network FDTD Method

    Page(s): 2023 - 2033
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    The lumped-network finite-difference time-domain (LN-FDTD) technique is an extension of the conventional FDTD method that enables the incorporation of linear one-port LNs in a single FDTD cell. This paper studies the stability and the numerical dispersion of this technique. To this end, an isotropic medium that is uniformly loaded with LNs in the x-direction is considered as a working model. The stability analysis, based on the von Neumann method, is performed for general Mth-order LNs and closed-form stability conditions are derived for some particular cases. The numerical dispersion relation is obtained for plane-wave propagation in the proposed LN-loaded medium. It is shown that LNs can be interpreted in terms of an effective frequency-dependent permittivity and, as a consequence, the LN-loaded medium can be viewed as a uniaxial medium. The numerical admittance of the LNs is also obtained showing that, as a side-effect of the time discretization, the LN parameters become frequency-dependent, e.g. for the resistor case, the resistance becomes a function of the frequency. View full abstract»

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  • Analysis and Regularization of the TD-EFIE Low-Frequency Breakdown

    Page(s): 2034 - 2046
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1320 KB) |  | HTML iconHTML  

    Low-frequency breakdown phenomenon plaguing marching-on-in-time solutions of time domain electric field integral equations is analyzed and cured. A theoretical analysis of the breakdown identifies deficiencies in the treatments proposed to date. A scheme for eliminating low frequency breakdown phenomena that leverages hierarchical regularization is presented. It applies to arbitrary meshes and gives rise to linear systems that are better conditioned than those obtained with standard loop-star/tree bases. The scheme's analytical properties and numerical results demonstrate its efficacy in accelerating the iterative solution of the time domain electric field integral equations. View full abstract»

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  • Analysis of Two Alternative ADI-FDTD Formulations for Transverse-Electric Waves in Lossy Materials

    Page(s): 2047 - 2054
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    A numerical dispersion analysis of the alternating-direction implicit finite-difference time-domain method for transverse-electric waves in lossy materials is presented. Two different finite-difference approximations for the conduction terms are considered: the double-average and the synchronized schemes. The numerical dispersion relation is derived in a closed form and validated through numerical simulations. This study shows that, despite its popularity, the accuracy of the double-average scheme is sensitive to how well the relaxation-time constant of the material is resolved by the time step. Poor resolutions lead to unacceptably large numerical errors. On the other hand, for good conductors, the synchronized scheme allows stability factors as large as 100 to be used without deteriorating the accuracy significantly. View full abstract»

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  • Spherical Vector Wave Expansion of Gaussian Electromagnetic Fields for Antenna-Channel Interaction Analysis

    Page(s): 2055 - 2067
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    In this paper, we introduce an approach to analyze the interaction between antennas and the propagation channel. We study both the antennas and the propagation channel by means of the spherical vector wave mode expansion of the electromagnetic field. Then we use the expansion coefficients to study some properties of general antennas in those fields by means of the antenna scattering matrix. The focus is on the spatio-polar characterization of antennas, channels and their interactions. We provide closed form expressions for the covariance of the field multimodes as function of the power angle spectrum (PAS) and the channel cross-polarization ratio (XPR). A new interpretation of the mean effective gains (MEG) of antennas is also provided. The maximum MEG is obtained by conjugate mode matching between the antennas and the channel; we also prove the (intuitive) results that the optimum decorrelation of the antenna signals is obtained by the excitation of orthogonal spherical vector modes. View full abstract»

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  • A Fast Algorithm for Computation of Electromagnetic Wave Propagation in Half-Space

    Page(s): 2068 - 2075
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (637 KB) |  | HTML iconHTML  

    A new frequency-domain algorithm, the planar Taylor expansion through the fast Fourier transform (FFT) method, has been developed to speed the computation of the Green's function related formulas in the half-space scenario for both the near-field (NF) and the far-field (FF). Two types of Taylor-FFT algorithms are presented in this paper: the spatial Taylor-FFT and the spectral Taylor-FFT. The former is for the computation of the NF and the latter is for the computation of the FF or the Fourier spectrum. The planar Taylor-FFT algorithm has a computational complexity of O(N2 log2 N2) for an N times N computational grid, comparable to the multilevel fast multipole method (MLFMM). What's more important is that, the narrowband property of many electromagnetic fields allows the Taylor-FFT algorithm to use larger sampling spacing, which is limited by the transverse wave number. In addition, the algorithm is free of singularities. An accuracy of -50 for the planar Taylor-FFT algorithm is easily obtained and an accuracy of -80 dB is possible when the algorithm is optimized. The algorithm works particularly well for narrowband fields and quasi-planar geometries. View full abstract»

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  • Electromagnetic Scattering From Arbitrarily Shaped Dielectric Bodies Using Paired Pulse Vector Basis Functions and Method of Moments

    Page(s): 2076 - 2083
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (498 KB) |  | HTML iconHTML  

    A pair of orthogonal pulse vector basis functions is demonstrated for the calculation of electromagnetic scattering from arbitrarily-shaped material bodies. The basis functions are intended for use with triangular surface patch modeling applied to a method of moments (MoM) solution. For modeling the behavior of dielectric materials, several authors have used the same set of basis functions to represent equivalent electric and magnetic surface currents. This practice can result in zero-valued or very small diagonal terms in the moment matrix and an unstable numerical solution. To provide a more stable solution, we have developed orthogonally placed, pulse basis vectors: one for the electric surface current and one for the magnetic surface current. This combination ensures strongly diagonal moment matrices. The basis functions are suitable for electric field integral equation (EFIE), magnetic field integral equation (HFIE), and combined field formulations. In this work, we describe the implementations for EFIE and HFIE formulations and show example results for canonical figures. View full abstract»

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IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

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Editor-in-Chief                                                 Kwok W. Leung